I'm working on an Arduino-based quadcopter project and want to add routing abilities to my project. I already have a slew of sensors up and working, so that leaves GPS.

Can someone recommend a relatively inexpensive, entry-level GPS unit? I'd prefer a shield, but any sort of rig works. I've been through SparkFun's collection, but was having a bit of trouble deciphering all the information.

I understand that the territory comes with a bit of a price tag, but I'm hoping to find something that works that doesn't completely eat my wallet.

From my experience running a team of engineers that developed, productionized, fielded, and supported a UAV system in a combat zone I have found GPS modules to be amazingly robust when it comes to mechanical shock. I have seem small UAVs landed into a concrete wall at full throttle and fly the same electronics in the same or another bird by a simple swap out. Note: UAV engineers often use the term land where a customer might make the mistake of saying crash.